1. Technical Field
The present invention relates to a thin film transistor substrate and a method of fabricating the same, and more particularly, to a display device including a thin film transistor substrate having a white pixel and a method of forming the same.
2. Discussion of the Related Art
Liquid crystal display (LCD) devices include a first substrate having a thin film transistor (TFT) thereon, a second substrate opposite the first substrate and having a color filter thereon and a liquid crystal layer interposed between the first substrate and the second substrate. The liquid crystal layer may have anisotropic dielectric properties. The LCD devices can display images by adjusting the amount of light transmitted through the liquid crystal layer by controlling an electrical signal applied to a common electrode and a pixel electrode formed on the first substrate and/or the second substrate.
Generally, the first substrate has a number of thin film transistors and the second substrate has a number of color filter patterns which may include a red color filter pattern, a green color filter pattern and a blue color filter pattern. To fabricate the LCD device, the first substrate and the second substrate are assembled, but during the assembly, the color filter pattern on the second substrate and the TFT on the first substrate can be misaligned. To reduce the misalignment, an assembly margin may be increased, but this can diminish a transmittance of the LCD devices. Conversely, the reduction of the assembly margin can increase the transmittance of the LCD devices. Fabricating the TFT and the color filter pattern on the same substrate in a color filter pattern on array (COA) structure can reduce the assembly margin and increase the transmittance of the LCD devices. In addition, forming a light blocking pattern on the first substrate can increase the transmittance of the LCD devices.
However, several photo mask steps are used to make the color filter patterns on the second substrate. Costs and turnaround times to fabricate the LCD devices may be in proportion with the number of steps of a photo lithography process. As a result, reducing the number of photo mask steps to fabricate the color filter patterns can reduce the costs and the turnaround times.
An inkjet printing method can reduce the number of photo mask steps for making the color filter patterns. For example, because the color filter patterns can be directly formed on a substrate by the inkjet printing method without having to use the photo lithography process, the costs and the turnaround times can be reduced.
To make high resolution displays, pixel sizes of the LCD devices have been reduced. However, because the transmittance of the LCD devices depends on the open ratio of the pixels and the transmittance of the color filter pattern, the reduction of the pixel sizes decreases the transmittance of the LCD devices. Moreover, the color filter patterns having a red color filter pattern, a green color filter pattern and a blue color filter pattern may only transmit 33% of incident light. To increase the transmittance of the high resolution displays, a white color filter pattern which transmits almost all of the incident light may be realized. However, the formation of the white color filter pattern adds another process step, and thus can increase the costs and turnaround times for the fabrication of LCD devices.
Accordingly, there is a need to increase the transmittance of an LCD device while reducing the costs and turnaround times for its fabrication.